Sample slide-deck for COGS End-of-Year Presentation Demo 1

1. Fix Contour Elevation Values
27 January 2012
Repair of ~14 500 Contour Elevation
Values in GIS.sde

2. The Problem …
In part of Kings County, a number of contour values are off by a factor
of 10 (rather than 2200 m, highest should be about 240 m). The culprits
appear on a TIN in reds, although values are 100 to 2200 m.
The next slides show how I fixed this; will update GIS.sde this morning.

3. The Problem
I created the TIN, using SDE-based contour lines
(still saved on SDE with Backup in feature class
name). Used “select features by rectangle” to
select contours on screen; unselected a few
with elevation < -5000 or > 5000 m.

4. How to Select “Wrong” Contours?
One can’t use select by attributes (ie elevation >
200) as, although the distinct border in northwest
is identified, a number of legitimate contours are
selected.

5. The Delimiters Dataset Helps
I used Definition Query of "FCODE" = 'DLNLOT' to
reduce the number of lines on the screen; then
used identify to determine the unique identifiers
(uses field DELIMITERS_) of the seven tiles.

6. Convert Delimiters into Polygons
Used Select By Attributes to select just seven tiles.
Then Feature-to-Polygon tool to convert to a
format suitable for overlay.

7. Dissolve to Make One Polygon
Used this “simple” (no optional parameters were
specified) dissolve to create one polygon. Will use
that polygon in select-by-location.

8. Select Contour Arcs
The select-by-location screen that selects contour
arcs that are within the dissolved delimiters.

9. Selected Candidate Contours

10. Tag Altered Contours; Set Elevation

11. Results: Look for Anomalies in TIN

12. TIN
This TIN shows a much nicer surface as there are
no wildly wrong elevation values.

13. Results
Contours have been re-written to GIS.sde: the
original (wrong) data is contours_arcBackup; and
new (repaired) data is contours_arc.
There are a few contours with +/- 217 000 000 m
as elevation; I will repair on a one-off basis.